How to not distort pixels?
The question about blurry textures has been asked countless times before, it has to do with the used texture sampling.
See this answer for more details https://blender.stackexchange.com/a/47643/19307

As for distorted (as in stretched or compressed) textures it all as to do with the way you UVMap your textures.

Fix your UV's so as not to cause distortions, evenly scaled islands and proportionally unwrapped faces will help. If possible use the UV Map > Cube Projection which will cause minimal distortion, or UV Map > Project From view

Alternatively consider using generated texture coordinates where possible instead. This may not work in the viewport or exported models.